A great variety of mattresses have been used by modern consumers. Among them the most popular nominal sizes are: king, queen, double, twin etc. Although, the peripheral dimensions of the mattresses in each nominal size category are constant, the thickness or depth dimensions of the mattresses even within the same category may differ substantially. For example, the thickness of the mattresses within the same nominal size can vary from about 5 inches to about 15 inches. Therefore, it is quite difficult to make a conventional mattress cover which fits all different thickness or depth dimensions of the mattresses in the same nominal group. In view of excessive material, a conventional cover does not typically fit tightly on a thin mattress, so that even with extensive tucking, such covers sag, wrinkle and hang loosely on the bed, often allowing the cover to slip relative to the mattress. On the other hand, a thick mattress typically requires extra material for the cover, so that it does not pull out from the underside of the mattress. Yet another problem with conventional, fitted mattress covers is the gathering of fabric in corner areas, resulting in the formation of sloppy looking wrinkled areas of material. This typically occurs when a conventional size cover is applied to a thin mattress. Furthermore, as a result of movement of the occupant of the bed of which the mattress forms a part, it is often quite difficult to prevent motion of the conventional mattress cover in general and its bottom portion in particular relative to the mattress.
Various approaches have been taken toward resolving the above-mentioned problems. For example, U.S. Pat. No. 5,249,322 to Seago provides a fitted mattress cover having a peripheral skirt which includes a layer of fabric material with a great plurality of parallel, spaced apart elastic cords stitched into the skirt fabric to gather the fabric material into folds positioned perpendicular to the longitudinal axis of the elastic cords. It is obvious from the disclosure of the Seago patent that manufacturing of such mattress cover in general and its skirt portion in particular is quite complicated, time consuming and significantly adds to the overall cost of this bedding feature.
U.S. Pat. No. 2,162,755 to Shauer et al. teaches a mattress covering bed sheet for preventing the formation of wrinkles as well as undesirable gathering of fabric. For this purpose, Shauer suggests use of triangular gussets situated at each corner of retaining flaps positioned on the underside of the mattress. However, the triangular gussets should be manually tucked and pulled when the sheet is applied in order to eliminate wrinkles and bunching of the fabric. Attaching of the gussets to the fabric of the bed covering sheet requires a laborious manufacturing operation. Finally, in view of a relatively stiff nature of material used for making the gussets, storage of this type of bed covers requires extra space and can be complicated.
Thus, there has been a considerable need for a universal, simple, inexpensive and reliable mattress cover which is capable of accommodating different thickness of the mattresses in the same nominal size category without resulting in a sloppy fit between the cover and the mattress.